The present invention relates to a device for heating the seams of tubular wrappers which surround rod-like fillers in machines for the production of rod-shaped articles which constitute or form part of smokers' products. More particularly, the invention relates to a device for promoting the setting of adhesive serving to connect the marginal portions of a tubular wrapper which consists of cigarette paper or the like and surrounds a rod-like filler of tobacco and/or filter material.
It is known to start various components of a cigarette making machine (or analogous machine for the production of rod-shaped articles which constitute or form part of smokers' products) at different stages of acceleration of the machine from zero speed to normal operating speed. Such stepwise or stagewise actuation of various components is desirable, especially if the machine forms part of a complete production line, in order to reduce the number of rejects during acceleration from zero speed to normal operating speed. A complete production line may comprise one or more machines for the production of plain cigarettes, one or more machines for the production of filter rod sections, one or more filter cigarette making machines, and one or more packing machines for filter cigarettes. One of the aforementioned components in a machine for the making of plain cigarettes, filter rod sections or filter cigarettes is the heating device which promotes the setting of adhesive that is applied by a suitable paster to bond the overlapping marginal portions of a web of cigarette paper or the like to each other. In a maker of plain cigarettes, the paster applies a film of adhesive to one marginal portion of a continuous cigarette paper web, and such marginal portion is thereupon folded over the other marginal portion so that the web is converted into a continuous tubular wrapper which surrounds a rod-like filler of tobacco particles. In a filter rod maker, the web (which may consist of paper, artificial cork or other suitable wrapping material) is converted into a tube which surrounds a rod-like filler consisting of fibrous filter material and/or other filter material or materials. In a filter cigarette making machine, the web is subdivided into adhesive-coated uniting bands which are used to bond filter rod sections to adjacent end portions of plain cigarettes.
The trend in the tobacco processing industry is toward higher operating speeds of machines which process tobacco and/or filter material. This necessitates a pronounced intensification of heating action in order to insure that the seam of the wrapper which surrounds a continuous rod-like filler of tobacco and/or filter material can resist the tendency of confined material to expand as well as that the seam is not caused to burst open when a wrapped tobacco filler or a wrapped filter material filler is severed to yield a succession of plain cigarettes or filter rod sections. However, pronounced intensification of heating action is likely to result in charring or discoloration of the seam, especially during the initial stage of operation subsequent to starting of the prime mover for a discrete machine, for certain machines of a production line, or for all machines of a production line. Heretofore known proposals to conform the intensity of heating action to changes in the speed of lengthwise movement of a tubular wrapper which surrounds a rod-like filler of tobacco or filter material failed to gain acceptance in the tobacco processing industry, primarily because the inertia of heating devices is too high to permit gradual intensification or gradual weakening of the heating action proportionally with changes in the speed of the filler. Such mode of operating the heating device of a cigarette maker or the like is satisfactory only when the acceleration of the machine to normal operating speed takes up a very long interval of time. This is undesirable because the acceleration stage invariably or almost invariably entails the production of rod-shaped articles which are or are likely to be defective, i.e., it is preferred to accelerate the machine to normal operating speed with a minimum of delay.